Analysis of Unsteady Flow Characteristics of Centrifugal Pump under Part Load Based on DDES Turbulence Model

Abstract

To better reveal the mechanism of the rotor-stator interference between the impeller and the guide vane and the evolution process of the stall vortex under the part-load conditions, numerical simulation is carried out based on the DDES turbulence model, which can better capture vortex structure. And the pressure pulsation and the radial velocity distribution of the centrifugal pump are studied. The vortex structure and pressure fluctuation of pump internal flow field under part-load condition of Q = 0.4 Qdes are mainly analyzed. The analysis results show that the stall vortex is formed at the inlet of the impeller and evolves to the outlet of the impeller, the front cover to the rear cover according to the fluid flow direction, and then disappears. Besides, under the part-load condition, the vorticity of the impeller outlet is always obviously less than that of the impeller inlet as the flow rate increases. Due to the asymmetric action of the volute, the radial velocity distribution law of flow channel C1 is different from other flow channels at different blade heights. By analyzing the radial velocity, the phenomenon that the jet-wake flow impacts the guide vane with the rotation of the impeller is the main reason for the rotor-stator interference. And large radial velocity gradients appear at the front and rear cover plates, which will cause high energy loss and reduce pump efficiency. Besides, the conclusion can be drawn that the region with the strongest rotor-stator interference is the inlet region of the guide vane suction surface. It also occurs near the volute tongue but is lower due to the effect of the guide vane. This research may serve as a reference for the safe operation of centrifugal pumps under part-load conditions.

State of the Art on Two-Phase Non-Miscible Liquid/Gas Flow Transport Analysis in Radial Centrifugal Pumps Part C: CFD Approaches with Emphasis on Improved Models

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“…have been used by the researchers for their research work. A lot of new turbulence models [39][40][41] have also been developed by various researchers which work well for some speci c areas of applications.…”

Flow Characteristics and Energy Loss of a Multistage Centrifugal Pump with Blade-Type Guide Vanes

“…Fukao et al [2] conducted a simulation work of a model inducer using the LES (Large Eddy Simultion) method and found that the backflow gradually extends upstream to the impeller inlet with the decreasing flow rate. Xin et al [3] analyzed the jet-wake flow structure at the impeller outlet and proposed that these structures would induce unstable vortices and produce periodic pressure and velocity fluctuations around the outflow of the impeller. Zhang [4] proposed that the jet wake phenomenon around the impeller outlet was gradually weakened through PIV (Particle Image Velocimetry) experiments on a centrifugal model pump.…”